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A question for my readers:

We all know that when used fuel is discharged from a reactor, it’s highly radioactive.

But exactly how radioactive? Considering, say, typical used uranium oxide PWR fuel material at a typical burnup, what is the activity of the used fuel at discharge, in terms of, say, curies per GWh, or curies per gram?

I’m looking for a specific number, like that – can anybody direct me to it?

6 Responses

The radiation dose measured at a distance of 30 cm from a used CANDU fuel bundle, is ~5000-6000 Sv/h at removal, ~500-600Sv/h after one day. One year following discharge, it would be about 50 – 60 Sv/h, and the level drops to about 1 Sv/h after 50 years, 0.3 Sv/h after 100 years, and less than 0.001 Sv/h after 500 years.

These are AECL’s numbers for a CANFLEX bundle removed from a CANDU-6. I have no numbers for any other type of reactor, sorry.

The name of the study is “Dose Rate Estimates from Irradiated LWR Fuel Assemblies in Air.” You can find two tables (pages 2 and 4) on how much radiation a person would receive based on how far they stand from a PWR or BWR fuel assembly and how long the assembly has been out of the reactor. Data is in rems/hour. This is a study NEI references for various things.

The radioactivity of 1 MT spent fuel (50 MWd/kgU burnup) discharged from a pressurized water reactor/PWR (4.5% initial enrichment) are approximately 214 MCi at discharge, 25 MCi after one week, 13 MCi after one month, and 3 MCi after one year, respectively.

The the thermal powers of 1 MT spent fuel (50 MWd/kgU burnup) discharged from a PWR (4.5% initial enrichment) are approximately 2 MW at discharge, 200 kW after one day, 100 kW after one week, and 13 kW after one year, respectively.